bpmn-engine/src/JavaScripts.js

BPMN 2.0 execution engine. Open source javascript workflow engine.

import { Script } from 'node:vm';

export default function Scripts(disableDummy) {
  if (!(this instanceof Scripts)) return new Scripts(disableDummy);
  this.scripts = new Map();
  this.disableDummy = disableDummy;
}

Scripts.prototype.register = function register({ id, type, behaviour, logger, environment }) {
  let scriptBody, language;

  switch (type) {
    case 'bpmn:SequenceFlow': {
      if (!behaviour.conditionExpression) return;
      language = behaviour.conditionExpression.language;
      if (!language) return;
      scriptBody = behaviour.conditionExpression.body;
      break;
    }
    default: {
      language = behaviour.scriptFormat;
      scriptBody = behaviour.script;
    }
  }

  const filename = `${type}/${id}`;
  if (!language || !scriptBody) {
    if (this.disableDummy) return;
    const script = new DummyScript(language, filename, logger);
    this.scripts.set(id, script);
    return script;
  }

  if (!/^(javascript|js)$/i.test(language)) return;

  const script = new JavaScript(language, filename, scriptBody, environment);
  this.scripts.set(id, script);

  return script;
};

Scripts.prototype.getScript = function getScript(language, { id }) {
  return this.scripts.get(id);
};

function JavaScript(language, filename, scriptBody, environment) {
  this.id = filename;
  this.script = new Script(scriptBody, { filename });
  this.language = language;
  this.environment = environment;
}

JavaScript.prototype.execute = function execute(executionContext, callback) {
  const timers = this.environment.timers.register(executionContext);
  return this.script.runInNewContext({ ...executionContext, ...timers, next: callback });
};

function DummyScript(language, filename, logger) {
  this.id = filename;
  this.isDummy = true;
  this.language = language;
  this.logger = logger;
}

DummyScript.prototype.execute = function execute(executionContext, callback) {
  const { id, executionId } = executionContext.content;
  this.logger.debug(`<${executionId} (${id})> passthrough dummy script ${this.language || 'esperanto'}`);
  callback();
};